It's very easy to scam thourgh these carts. Since he has the codes also, it is recommend to use the pins immeaditly, but it's rather hard to get them straight into your paypal. You will have to contact a converter-guy (which means extra costs)

1) No it's not, if that person has so much many in a PaySafeCard (PSC), something is wrong, because it's weird having so much money and not being able to use a credit card.

It's basically a prepaid-card system for kids or people who can't use a credit card to buy stuff online (you go to a shop, buy the prepaid card with money and use it online). Not many (international) places accept those, if any, because it envolves fees. I've used them several times (on Steam and europen online key stores) and it's safe to use, but that amount of money is ridiculously big to be "real".

2) You can't, you can only "trade it with a converter-guy".
3) Nope.

While I've never used or heard about PaySafeCard before today, I've seen several similar payment services. Often in cases like these, the scammer relies on you not having heard about the payment system, and thinking it's a "safer alternative to PayPal". Unless you have a really good reason to believe he's legit, you'll probably learn about chargeback scams the hard way if you accept.

Here's a fun experiment: Tell him to buy keys with that money, and see what he says. I almost guarantee you he'll try to make up an excuse as to why he won't and it's his way or you get nothing. He'll then try to pressure you into doing it his way by saying if you don't hurry up he'll leave, or that he has something to do. If he really wanted the hat (which he'd have to if he were spending more than $100 on it), he wouldn't leave that quickly, and for that amount of money he'd understand you taking precautions. If he leaves, you just shooed away a scammer and you should feel proud.